Treated red lead



United States Patent ()fihce Patented May 23, 1961 3- c tl m r .(C 10 9length of time of said paint.

Although red lead is" one of the mo t p p la nd useful anti-corrosionpigments on the market, paints made An object of this inventiontherefore, is to provide an improved red lead pigment.

conta n and the tendency of of tetracarboxybutane, .tetracarboxyhutane.a

'In .a particularlydesirable embodiment, this invention contemplates acomposition as aforesaid wherein there and a mixture of litharge andpresent, but there is no particular advantage in employing such anexcess. Less than 15% of the lead salt of tetracarboxybutane may bepresent and still provide beneficial eflects.

Not only are the anti-corrosive properties of a red lead paint retainedwhen a increasingly viscous upon I The mechanism of this suppression ofthe tendencies of the paint to become viscous upon standing and tosettle and form a hard mass is not fully understood.

' The lead salt of tetracarboxybutane may be prepared by reactingtetracarboxybutane' the red lead pigment and then incorporating thispiginitially reacting the litharge present with the tetracarboxybutane,care being taken to insure that enough PbO is also present to react withthe tetracarboxybutane presformulated into a paint. present in the redlead is such,

kn w a ve ug y occur- Th s liven'n en e y y be prevented by neutralizingthe excess PbO with addit o a et ac rb x bl tane or example, o in meother np n manne n rder to more fu i us ra he a re o s i en ion d th qraq icins t s m h fo owing examp s a e s nted.-

7 Example 1 The redlead used in this example was a low PbO red leadprepared by the furnace process and containing 2.98% by weight of P1 0.Two thousand grams of this lead containing 59.6 grams of PhD (0.267 mol)were suspended in two liters of distilled water and the suspensionstirred vigorously by means of a mechanical stirrer. Then 31.3 grams0.134 mol) of l,2,3,4-tetracarboxybutane in powdered :form wereintroduced over a five-minute interval. Agitation was continued for anadditional /2 hour after which the suspension was allowed to settle Ov nht and n fi ter n a Bi c n nnn filtered cake was washed with distilledwater until the filtrate had a substantially neutral pH. The washedfilter cake was then o en u an d d a 51 and oun a hammer sni Example 11The rrsqe lu l fixam le re ea w n ha no water was used,'and the mixturewas dry ground together in a ball mill until the mixture was uniform.

Example III A paint using the pigment prepared according to Example Iwas formulated as follows:

Percent Pigment 70.4

0 Vehicle 29.6

which is a medium length linseed oil alkyd resin and 16.34% of Sovasol#5, which is an aliphatic petroleum mineral spirits.

A control was prepared in exactly the same manner except that thepigment contained no tetracarboxybutane or lead salt oftetracarboxybutane. The 70.4% of the control pigment contained 2.98%PbO, and 97.02% of Pb O Both paints were allowed to stand for 36 days,and the consistency of both conclusion thereof. The consistencymeasurements were accomplished via A.S.T.M. consistency test methodD-562-55. At the end of the 36 day period, the control containing nolead salt of tetracarboxybutane had a consistency of 435 grams, whilethe paint wherein a lead salt of textracarboxybutane was used had aconsistency of 280 grams. The original consistency of the control was330 grams, and the original consistency of the paint containing a leadsalt of tetracarboxybutane was 250 grams.

Example IV A control, identical with control of prepared except that the70.4% of pigment of 3.05% PbO, and 96.95% of Pb O A pigment was preparedaccording to the process of this invention, and in particular, in themanner of Exame ple I except that 3.05% of PhD was used and acorrespondingly larger stoichiometric amount of tetracarboxybutane wasused. The formulation of the paint was the same as in Example I.

A second pigment was prepared according to the process of thisinvention, and in particular, in the manner of Example 11. The pigmentwas prepared by dry mixing 3.05% PbO, 96.95% of Pb O and astoichiometric amount of tetracarboxybutane was used, saidstoichiometric amount based on the amount of PbO present. A paint wasformulated in the manner of Example III, that is 70.4% of the pigmentmixture containing the tetracarboxybutane and 29.6% of vehicle.

All the three paints were allowed to stand for 36 days. It was foundthat at the end of 36 days, the control had a harder cake at the bottomof the paint receptacle then either of the other two paints whichcontained the treated pigment, treated according to Example I and thepigment prepared according to Example II. Both of thesetetracarboxybutane treated pigments exhibited a very soft settlingtendency of approximately one-eighth of an inch in height.

Example III was was composed Example V A control was prepared accordingto Example control contained 11.3% of PhD, and 88.7% of Pb O A paint wasformulated in the manner of formulation of the control of Example HI.

A pigment was prepared in the manner of Example II, except that therewas present 11.3% of PhD, a stoichio metric amount oftetracarboxybutane, and the remainder was Pb O A paint was preparedusing the formulation of Example III, that is 70.4% of the mixtureprepared according to Example II, and 29.6% of the vehicle.

The consistency of the paints was measured at the conclusion of the 36day period and one day after the paints were prepared. The method usedwas the same as in Example III, that is A.S.T.M. D-562-55 consistencytest III. This paints was measured at the:

method. The initial consistency of the control was 350 grams. The finalconsistency of the control was 700 grams. The initial consistency of thepaint prepared according to this invention was 310 grams. The finalconsistency of the paint prepared according to this invention was 485grams.

As is obvious from the foregoing examples, a pigment prepared accordingto the process of this invention when utilized in paints shows a markedeffect in suppressing the tendency of the pa'nt to become viscous uponstanding and suppresses the tendency to harden into a solid mass at thebottom of the paint receptacle. The suppression of these tendenciesshould result in paints with a .longer shelf life, and in a moreconsistent, uniform, and dependable product. The process itself, is asimple one and can readily be carried out by an operator without specialskill or training.

In addition, as an interesting side note to this invention, thecompositions according to this invention seem to show a marked abilityto eliminate the livering problem present in red lead anti-corrosionpaints.

While this invention has been described in terms of certain preferredembodiments and illustrated by means of specific examples, these areillustrative only, and the invention is not to be construed as limited,except as set forth in the following claims.

I claim:

l. A pigment composition consisting essentially of red lead, and atleast one additive selected from the class consisting of a lead salt oftetracarboxybutane, and a mixture of litharge and tetracarboxybutane,said additive being present in the amount of from 4.24% to about 15% byweight based on the combined weight of said red lead and said additive;said litharge and said tetracarboxybutane being present in theproportion of at least 1 mole of tetracarboxybutane per 2 moles oflitharge.

2. A method of suppressing the tendency of a red lead pigment to settlein a paint vehicle, and the tendency of the paint to become increasinglyviscous which comprises adding to said red lead pigment, at least oneadditive selected from the class consisting of a lead salt oftetracarboxybutane, and a mixture of litharge and tetracarboxybutane,said additive being; present inthe amount of from 4.24% to about 15% byweight based 'on the combined weight of said red lead and 1 saidadditive; said litharge and said tetracarboxybutane being present in theproportion of at least 1 mole of tetraearboxybutane per 2 moles oflitharge.

3. A paint composition containing a pigment composition according toclaim 1.

References Cited in the file ofthis patent UNITED STATES PATENTS2,182,436 Johnstone Dec. 5, 1939 ,2,236,296 Minich et al Mar. 25, 19412,836,483 Schulz May 27, 1958 FOREIGN PATENTS j 26,322" Great Britain.Oct. 2, 1897 264,492 Great Britain Feb. 9, 1928 Australia Aug.

1. A PIGMENT COMPOSITION CONSISTING ESSENTIALLY OF RED LEAD, AND ATLEAST ONE ADDITIVE SELECTED FROM THE CLASS CONSISTING OF A LEAD SALT OFTETRACARBOXYBUTANE, AND A MIXTURE OF LITHARGE AND TETRACARBOXYBUTANE,SAID ADDITIVE BEING PRESENT IN THE AMOUNT OF FROM 4.24% TO ABOUT 15% BYWEIGHT BASED ON THE COMBINED WEIGHT OF SAID RED LEAD AND SAID ADDITIVE,SAID LITHARGE AND SAID TETRACARBOXYBUTANE BEING PRESENT IN THEPROPORTION OF AT LEAST 1 MOLE OF TETRACARBOXYBUTANE PER 2 MOLES OFLITHARGE.